Exemplary embodiments of the invention include a method of operating an aircraft headlight system of an aircraft, the aircraft headlight system having at least one headlight, wherein the method comprises the steps of operating the aircraft headlight system in a landing light mode during a descent of the aircraft, with the at least one headlight emitting a landing light output in the landing light mode; operating the aircraft headlight system in a taxi light mode during taxiing of the aircraft, with the at least one headlight emitting a taxi light output in the taxi light mode; and transforming the landing light output into the taxi light output after touch-down of the aircraft by operating the aircraft headlight system in at least one intermediate lighting mode between operating the aircraft headlight system in the landing light mode and operating the aircraft headlight system in the taxi light mode.
Exemplary embodiments of the invention allow for the switching from a landing light mode to a taxi light mode after touch-down of the aircraft in a manner that is little disruptive to the pilots' awareness of the environment on the runway/airfield. In particular, a hard switch between the landing light mode and the taxi light mode, which results in an abrupt change of the illumination of the aircraft environment and thus poses a large burden on the pilots' eyes in terms of adapting to the changed illumination, may be prevented by transforming the landing light output into the taxi light output via at least one intermediate lighting mode. The transforming of the landing light output into the taxi light output via one or more intermediate lighting modes may provide for a soft transition between the landing light mode and the taxi light mode. In this way, the pilots' eyes may more easily adapt to various smaller steps/changes in the light output, as compared to a big step between the landing light output and the taxi light output. In this way, the operating safety of the aircraft may be increased, because the pilot can have a more uninterrupted awareness of the aircraft environment due to the eyes adapting faster to smaller changes in the light output of the aircraft headlight system.
The aircraft headlight system is operated in at least one intermediate lighting mode between operating the aircraft headlight system in the landing light mode and operating the aircraft headlight system in the taxi light mode. Each of the at least one intermediate lighting mode has a respective intermediate light output, which is emitted by the at least one headlight in the at least one intermediate lighting mode. In terms of the output light intensity distribution, the at least one intermediate light output is more similar to the landing light output and to the taxi light output than the landing light output is to the taxi light output. In other words, the similarity in output light intensity distribution between each of the at least one intermediate light output and the the taxi light output is greater than the similarity in output light intensity distribution between the landing light output and the taxi light output. Analogously, the similarity in output light intensity distribution between each of the at least one intermediate light output and the the landing light output is greater than the similarity in output light intensity distribution between the landing light output and the taxi light output. The similarity between two output light intensity distributions may be calculated as the integral over the difference between the output light intensity distributions in question or by any other suitable measure. The above described relations for the similarities between the output light intensity distributions in question is reflected by the term intermediate lighting mode, which indicates a middle state between the landing light mode and the taxi light mode, as well as the term transforming the landing light output into the taxi light output, which indicates a targeted adaptation towards the taxi light output.
The aircraft headlight system is operated in a taxi light mode during taxiing of the aircraft. While the term taxi light mode is used, this taxi light mode may also be referred to as a combined taxi and runway turn-off light mode. During taxiing of the aircraft, the aircraft headlight system may carry out both the functions of a more forward-directed ground illumination light, sometimes referred to as taxi light in a narrow sense, and a more sideway-directed/angled ground illumination light, sometimes referred to as runway turn-off light.
The operating of the aircraft headlight system in the taxi light mode, as described above, may take place after the operating of the aircraft headlight system in the landing light mode during the descent of the aircraft. In other words, above references to the operating of the aircraft headlight system in the taxi light mode may refer to the operation of the aircraft headlight system after landing. Accordingly, the step of operating the aircraft headlight system in the taxi light mode may refer to the taxiing from the runway towards the gate. As a consequence, the step of transforming the landing light output into the taxi light output may refer to the operation of the aircraft headlight system after landing and before reaching a state of continuous ground illumination for the taxiing on the airfield.
According to a further embodiment, that step of transforming the landing light output into the taxi light output lasts between 3 s and 10 s. In a particular embodiment, the step of transforming the landing light output into the taxi light output lasts between 4 s and 7 s. Further in particular, the step of transforming the landing light output into the taxi light output may last about 5 s. This metric is defined as the duration of the one or more intermediate lighting modes being present, i.e. as the duration between the end of the landing light mode and the beginning of the taxi light mode. The given durations have been found to provide a transition between the landing light mode and the taxi light mode that is pleasing to the pilots' eyes and that allows for a gradual adaptation with a low level of disturbance to the pilots. Also, the given durations are a good compromise between a pleasing transition from the landing light mode to the taxi light mode and a responsive behavior of the aircraft headlight system in response to the touch-down or in response to an according pilot command.
According to a further embodiment, the at least one intermediate lighting mode comprises a sequence of a plurality of intermediate lighting modes, with an intermediate output light intensity distribution of each of the plurality of intermediate lighting modes having a wider horizontal illumination angle than a respectively preceding one of the plurality of intermediate lighting modes. In this way, the landing light mode, having a comparably narrow horizontal opening angle, may be transformed into the taxi light mode, having a comparably wide horizontal opening angle, in a plurality of steps. In this way, the horizontal illumination angle is broadened in a plurality of steps, thus allowing for an easy adaptation of the pilots' eyes to becoming aware of a wider portion of the aircraft environment over time. It is pointed out that it is also possible that additional intermediate lighting modes are present that are not associated with a broadening of the output light intensity distribution. The described sequence of intermediate lighting modes with an increasing horizontal illumination angle may for example be a subset of the entirety of intermediate lighting modes.
According to a further embodiment, the intermediate output light intensity distribution of each of the plurality of intermediate lighting modes has a lower peak light intensity than the respectively preceding one of the plurality of intermediate lighting modes. In this way, a particularly effective adaptation of the pilots' eyes to the changing light output may be achieved, because the human eye tends to focus on the spots of brightest illumination and areas of similar illumination. By gradually decreasing the peak light intensity, the pilots' eyes are slowly adjusted to regions of lower illumination in a step-by-step process.
According to a further embodiment, the aircraft headlight systems has a take-off light mode and the at least one intermediate lighting mode comprises the take-off light mode. In particular, a take-off light output may be emitted by the aircraft headlight system in the take-off light mode. In this way, the transformation of the landing light output into the taxi light output passes through the take-off light output, thus making use of a light mode that is also used at other operation times, in particular right before and/or after take-off. By using the take-off light mode as one of the one or more intermediate lighting modes, the number of different light modes may be kept small and an efficient implementation of the aircraft headlight system and its operating methods may be achieved.
According to a further embodiment, the taxi light output has a horizontal taxi light illumination distribution that is between a reference cosine distribution around a straight ahead direction of the aircraft and the reference cosine distribution, multiplied by three. In this way, a particularly pleasing taxi light output may be achieved that has limited variations for each horizontal viewing angle with the straight ahead direction. Said horizontal taxi light illumination distribution may be present for a limited horizontal opening angle. For example, it may be present within an opening angle of at least +/−60° with respect to the straight ahead direction of the aircraft. Further in particular, it may be present for a horizontal opening angle of between +/−60° and +/−80° with respect to the straight ahead direction of the aircraft. In a particular embodiment, the reference cosine distribution may be in accordance with the formulaE(α)[lx]=cos(α*1.145)*Enom.
According to a further embodiment, a vertical change of a peak intensity direction of the aircraft headlight system during the transforming of the landing light output into the taxi light output is between 2°/s and 8°/s, in particular between 2.5°/s and 3.5°/s, more in particular about 3°/s. In this way, the direction of peak intensity may rotate vertically in a manner similar to the rolling of the aircraft after touch-down. In this way, the adaptation of the light output may be particularly pleasing to the pilots' eyes, because the rotation of the peak intensity direction of the aircraft headlight system offsets the rolling of the aircraft, at least to some extent. It is pointed out that the vertical change of the peak intensity direction may be present during part of the transforming only. For example, the vertical change of the peak intensity direction may take place during a first phase of the transforming. Above described broadening of the output light intensity distribution may take place thereafter, with the peak intensity direction not experiencing a further change.
According to a further embodiment, the at least one intermediate lighting mode consists of at least three intermediate lighting modes, in particular of between three and fifteen intermediate lighting modes, further in particular of between five and ten intermediate lighting modes. In this way, a granular transition of the light output of the aircraft headlight system may be achieved, without causing excessive complexity for the operation of the aircraft headlight system. For each of the plurality of intermediate lighting modes, the similarity in output light intensity distribution to the preceding intermediate lighting mode and to the taxi light mode may be greater than the similarity in output light intensity distribution between the preceding intermediate lighting mode and the taxi light mode. In this way, an overall convergent transformation may be achieved.
Exemplary embodiments of the invention further include an aircraft headlight, configured for being mounted to an aircraft for illuminating an aircraft environment, the aircraft headlight comprising an LED group, comprising a plurality of LEDs, and an optical system, comprising at least one optical element, the optical system being associated with the LED group for shaping a light output from the light emitted by the LED group, wherein the LED group and the optical system are stationary within the aircraft headlight, with each LED of the LED group having a set position with respect to the optical system, wherein the aircraft headlight is configured to be operated in a landing light mode having a landing light output, a taxi light mode having a taxi light output and at least one intermediate lighting mode having at least one intermediate light output, with a respective subset of the plurality of LEDs being switched on in each of the landing light mode, the taxi light mode and the at least one intermediate lighting mode, and wherein the aircraft headlight is configured to transform the landing light output into the taxi light output by operating in the at least one intermediate lighting mode between operating in the landing light mode and operating in the taxi light mode. The additional features, modifications, and effects, as described above with respect to the method of operating an aircraft headlight system comprising an aircraft headlight, apply to the aircraft headlight in an analogous manner.
According to a further embodiment, the plurality of LEDs are dimmable. In addition to the plurality of LEDs being individually switchable between an on state and an off state, which allows for respective subsets to be switched on for the different operating modes, the plurality of LEDs being dimmable provides for additional degrees of freedom for designing the one or more intermediate lighting modes. The transforming of the landing light mode into the taxi light mode may be provided in a particularly granular and pleasing manner in this way.
According to a further embodiment, the aircraft headlight is configured to transform the landing light output into the taxi light output by operating in at least three intermediate lighting modes, in particular in between three and 15 intermediate lighting modes, further in particular in between five and ten intermediate lighting modes, between operating in the landing light mode and operating in the taxi light mode.
According to a further embodiment, the aircraft headlight is configured to transform the landing light output into the taxi light output over a transformation interval of between 3 s and 10 s, in particular of between 4 s and 7 s, further in particular of about 5 s.
According to a further embodiment, the aircraft headlight further comprises a control unit, wherein the control unit is configured to switch on the respective subsets of the plurality of LEDs in accordance with the landing light mode, the taxi light mode and the at least one intermediate lighting mode. In other words, the control unit is configured to individually control the plurality of LEDs in accordance with a momentarily desired light mode. In particular, the control unit may be configured to switch on/off particular subsets of LEDs and, if applicable, dim particular ones of the LEDs. The control unit may be configured to cause a set sequence of landing light mode, at least one intermediate lighting mode, and taxi light mode, with each of the at least one intermediate lighting mode having a set duration. The control unit may have a control input for receiving a pilot signal for starting the set sequence and/or for receiving an aircraft generated signal indicating the touch-down of the aircraft for starting the set sequence.
Exemplary embodiments of the invention further include an aircraft comprising at least one aircraft headlight, as described in any of the embodiments above. The additional features, modification, and effects, as described above with respect to the aircraft headlight, apply to the aircraft in an analogous manner. The aircraft may be an airplane or a helicopter.
According to a further embodiment, the aircraft, in particular an airplane, comprises one or two or three or four aircraft headlights, forming an aircraft headlight system of the aircraft. In a particular embodiment, the aircraft headlight system consists of three aircraft headlights, with a first aircraft headlight being mounted to a front running gear of the aircraft and a second and third aircraft headlights being mounted to a left wing root section and a right wing root section of the aircraft, respectively. Jointly providing the light modes via multiple headlights, such as the described three headlights, has been found to be a good compromise between complexity of the individual headlights and complexity of adapting and synchronizing the multiple headlights with respect to each other.